Blood Vessels

Question 1

Describe continuous endothelium?

Answer 1

Endothelial cells which form a continuous sheet around lumen of vessels. The
only gaps are between adjacent endothelial cells. Found in muscle, skin, lung,
connective tissue

Question 2

Describe fenestrated endothelium

Answer 2

Endothelial cells contain perforations of 50 - 60 nm. More permeable
than continuous endothelial cells. Found in kidney and villi of intestine

Question 3

Describe discontinuous endothelium

Answer 3

endothelial cells have gaps up to 100 nm wide. Found in spleen and
liver.

Question 4

What seperates the lumenal surface of endothelial cells from the lumen of blood vessels?

Answer 4

Glycocalyx, anegatively-charged complex of proteoglycans and glycosaminoglycans. It extends from 20 to 3000 nm off the luminal surface of endothelial cells. Appears to form a mesh with 20 nm spacing that may function as molecular sieve. Its negative charge impedes passage of negatively-charged (acidic) proteins.

Question 5

What proteins anchor endothelial cells in blood vessels to the basement membrane?

Answer 5

Integrins

Question 6

Name 3 compounds that induce gap junctions between adjacent endothelial cells

Answer 6

thrombin (as part of coagulation cascade), bradykinin (a dilatory factor), and histamine (as part of the inflammatory response)

Question 7

How are gaps introduced between adjacent endothelial cells?

Answer 7

2 ways: disruption of proteins making up gap junction (occludins, claudins, and cadherins) or contraction of endothelial cells (by thrombin, very similar to muscle contraction)

Question 8

What are selectins?

Answer 8

Proteins on the surfaces of leukocytes and endothelial cells. They generate adhesive forces between the two, and are expressed on endothelial cells in response to inflammatory factors

Question 9

What are ICAM and VCAM?

Answer 9

Proteins expressed on endothelial cells in response to chemokines and chemoattractants. They tightly bind integrins on leukocytes as part of the arrest interaction

Question 10

How do leukocytes exit blood vessels?

Answer 10

They activate the contraction of myosin filaments which pulls apart junctional complexes between endothelial cells. Leukoctyes then slide between endothelial cells, binding to different endothelial
junctional proteins

Question 11

How does VEGF (Vascular endothelial growth factor) trigger angiogenesis?

Answer 11

VEGF causes endothelial cells to loosen connections with neighboring cells,
dissolve surrounding basement membrane and reverse polarity. Activated endothelial cells extend filopodia along VEGF gradients and also follow other guidance factors. Upon reaching a target vessel, migrating endothelial cells reestablish contacts and
form the lumen of the new vessel.

Question 12

What are the three layers of blood vessels?

Answer 12

The tunica intima, media, and adventitia

Question 13

Describe the tunica intima

Answer 13

The tunica intima comprises the endothelium, the adjacent basement membrane, the subendothelial connective tissue, and the internal elastic lamina; in smaller vessels, pericytes appear between layers of the split basement membrane of the endothelium

Question 14

Describe the tunica media

Answer 14

The tunica media is composed of smooth muscle cells, elastic lamellae including the external elastic lamina and collagen fibers.

Question 15

Describe the tunica adventitia

Answer 15

The tunica adventitia contains connective tissue, a few cells, macrophages, mast cells, fibroblasts, and the nerves and vessels that supply the vascular wall.

Question 16

What is characteristic of elastic arteries?

Answer 16

Numerous concentric elastic lamellae of the tunica media interspersed with bundles of 2
smooth muscle cells. Elastic fibers in the media allow for the maintenance of blood pressure through the expansion and contraction of the vessel walls. Contains a vasa vasorum in their adventitia and outer part of the media

Question 17

What is a vasa vasorum?

Answer 17

a network of small vessels that supplies the cells of larger vessels

Question 18

Describe the tunica of the muscular arteries

Answer 18

The media of muscular arteries is composed of many concentric layers of smooth muscle cells arranged in a low angle helix, interspersed with less frequent and sometimes discontinuous elastic lamellae. The internal elastica marks the conventional boundary between intima and media. The external elastica separates the media from the adventitia. The media and adventitia of muscular arteries are approximately equal in
thickness.

Question 19

What is the difference between arterioles and muscular arteries?

Answer 19

Arterioles contain no external elastic lamina, and the adventitia consists of a thin layer of collagen and isolated elastic fibers, whereas muscular arteries have adventitia as large as their media

Question 20

What are sinusoids?

Answer 20

Capillaries with a discontinuous endothelium

Question 21

What are pericytes?

Answer 21

contractile cells with long, branching processes that are

involved in the control of blood as it flows through the microvasculature, esp venules

Question 22

What is diapedesis and where does it occur?

Answer 22

It is the exit of leukocytes from vasculature, and it occurs in venules, at labile junctions

Question 23

What is special about vessels in the brain?

Answer 23

These arteries are rather thin-walled for their caliber, with a well-developed internal elastica and virtually no elastic fibers in the rest of the vascular wall. The veins have a thin wall devoid of smooth muscle cells.

Question 24

What is special about pulmonary vessels?

Answer 24

These arteries have thin walls as a result of a significant reduction in both muscular and elastic elements, while the veins have a well-developed media of smooth muscle cells.

Question 25

What is special about the umbilical vessels?

Answer 25

These arteries have two layers of smooth muscle cells without a prominent internal elastica or adventitia. The vein has a thick muscular wall with two to three muscle layers